Heretofore, a small-sized line thermal printer is widely used for a portable electronic device such as a receipt issuing machine.
As this type of thermal printer is required to be readily portable, a small-sized, light one is desired.
Therefore, heretofore, a body frame is made of metal such as a thin steel plate and a paper guide made of plastic for guiding recording paper to a printing part between a platen roller and a thermal head is installed as disclosed, for example, in Unexamined Japanese Patent Application No. Hei. 4-140175.
In such a thermal printer, a platen roller 104 and a head support part 103 are secured to a body frame 102 made of plastic as shown in FIG. 6, for example. Predetermined printing is executed on thermal recording paper by attaching a thermal head 130 on the side of the platen roller 104 of the head support part 103 so that thermal recording paper is held between the thermal head and the platen roller and by pressing the thermal head 130 attached to the head support part 103 on the platen roller 104 by a torsion coil spring 107.
There is also another conventional thermal printer in which a body frame is formed integrally with a paper guide from plastic material such as polycarbonate.
However, in such conventional type thermal printers, there are the following problems:
That is, in the case of the above conventional type thermal printers, as the paper guide 121 is made of plastic material, a charge cannot be discharged from the paper guide if thermal recording paper 100 is electrified, and the thermal head 130 may be broken by a spark and others.
Further, as the paper guide 121 is also electrified, there is a problem that the thermal recording paper 100 cannot be guided to the vicinity of the thermal head 130 and the thermal recording paper is hard to insert.
As the platen roller 104 is arranged apart from the bottom of the printer in view of space for gears for driving the platen roller, the paper guide 121 cannot be formed as a part of the body frame 102. Therefore, as the paper guide 121 is made of another member, the number of parts is increased and as a result, the cost is increased.
Even if the paper guide 121 is formed as a part of the body frame 102, there is also a problem that it is difficult to increase an angle at which thermal recording paper 100 is wound on the platen roller 104 and precision in feeding paper is not satisfactory.
Furthermore, if the body frame is also made of plastic material as in the other conventional types, the frame must be formed relatively thick to enhance rigidity. As a result, miniaturization cannot be sufficiently achieved.